1. Field of the Invention
The present invention relates to manufacturing of light guide plates, and particularly to a method for manufacturing a light guide plate using a duly manufactured mold.
2. Description of the Prior Art
Liquid crystal displays (LCDs) are now in widespread use in various applications; for example, in desktop computers, portable computers, LCD televisions, portable telephones, etc. An LCD cannot itself emit light. A light source system such as a back light system is needed for emission of light. A light guide plate is an important part of a back light system, because it controls uniform directionality of emitted light.
FIGS. 8A to 8K represent a conventional process for manufacturing a light guide plate, as disclosed in U.S. Pat. No. 6,522,373 issued on Feb. 18, 2003. The process includes the steps of:                a) applying a primer on a silicon substrate 10 covered with a silicon oxide (SiO2) film 11 to thereby enhance adhesion of a photo resist on the silicon oxide film, and forming a layer of photo-resist 12 on the silicon substrate 10 (FIG. 8A);        b) disposing a photo mask 13 having a pattern of concave small dots onto the silicon substrate 10, irradiating the silicon substrate 10 with ultraviolet (UV) rays from above the photo mask 13, and developing the photo-resist 12 to thereby form a pattern of concave small dots in the photo-resist 12 (FIG. 8B);        c) attaching a protective tape 14 onto an undersurface of the silicon substrate 10, and etching the silicon oxide film 11 to thereby form a pattern of concave small dots in the silicon oxide film 11 (FIG. 8C);        d) removing residual photo-resist 12 (FIG. 8D);        e) anisotropically etching a surface of the silicon substrate 10, with the silicon oxide film 11 functioning as a mask (FIG. 8E);        f) removing the protective tape 14, and removing the silicon oxide film 11 (FIG. 8F);        g) forming a conductive film 15 on the silicon substrate 10, for metal plating (FIG. 8G);        h) applying a metal plating onto the conductive film 15 as an electrode, and then separating the metal plating from the conductive film 15 to thereby obtain a master stamper 16 (FIG. 8H);        i) forming a very thin separator layer on an undersurface of the master stamper 16, plating the master stamper 16 at the separator layer, and then separating the plating from the master stamper 16 to thereby obtain a mother stamper 17 (FIG. 8I);        j) forming a very thin separator layer on a main surface of the mother stamper 17, plating the mother stamper 17 at the separator layer, and then separating the plating from the mother stamper 17 to thereby obtain a molding stamper 18 (FIG. 8J); and        k) polishing a dot-forming surface of the molding stamper 18, polishing an opposite undersurface of the molding stamper 18, attaching the molding stamper 18 to injection molding equipment, and performing injection molding to thereby obtain a light guide plate 1 (FIG. 8K).        
A pattern of concave small dots is thus formed in a main surface of the light guide plate 1. Each small dot defines a short side and a long side. A length of each short side is in the range from 10 to 100 μm. A length of each long side is at least 1.5 times the length of each short side, and no greater than 500 μm. Notably, when the length of each short side is greater than 10 μm, uniform luminance and color of the light guide plate tends to be reduced. In addition, the process for manufacturing the light guide plate 1 is complex. It takes three plating steps in order to form the master stamper, the mother stamper and the molding stamper. Then the molding stamper is used to finally obtain the light guide plate 1. All these processes are also time-consuming.
Therefore, it is desired to provide a new method for manufacturing a light guide plate which overcomes the above-described disadvantages of conventional processes.